Higher HR During Evening Workouts

I’ve noticed that while doing workouts in the evening after I get home from work around 5-7pm (I have an office job and spend most of my days in meetings and behind a computer), my heart rate is ~10-15% higher than if I did the same workout first thing in the morning. I’ve also noticed that in the evening, my HR will begin to decline for similar effort (negative decoupling) after 30 or so minutes.

I wonder what might be causing this and whether anyone else has had a similar experience.

Yes, lower HR in the morning. Yes, in the afternoon I often see HR decline after 20-30 minute warmup. I haven’t done any trend analysis, and don’t know if its 10-15% higher in the afternoon. And I don’t know if its due to the increase in outside temperature, as I mostly train outside. My lowest HR is usually when temperatures are 50-60F / 10-16C.

Edit: doing a quick spot check, afternoon average HR for endurance rides is about 2-3bpm higher. Its only a couple percent.

Stress from work in your system.

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How’s your caffeine intake? If I do an early morning workout without caffeine my HR is much lower than later in the day with (too much) coffee onboard.

I hadn’t considered the temperature but this time of year, there’s not much of a temp deviation in my garage. I also do most of my training outside and now that you mention it, I have noticed my afternoon outside training rides have a higher HR pretty much from the moment I roll out of the driveway.

I considered that but my job has been pretty low-stress lately. It’s common for my ‘Body Battery’ reading on my Garmin watch to increase during the workday.

This could definitely be a factor. I always have a black coffee before my morning rides and will have another cup or two after a morning ride but cut off caffeine after lunch.

I also wonder if it might be a circulatory issue as in addition to the higher HR, I’ve also noticed occasional numbness in the nether regions in the afternoon that doesn’t occur in the morning.

I guess what I’m really curious about is whether this is common or if it’s something to investigate further.